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Abstract

Background

Walking is the primary focus of population-based physical activity initiatives but
a theoretical understanding of this behaviour is still elusive. The purpose of this
study was to integrate personality, the perceived environment, and planning into a
theory of planned behaviour (TPB) framework to predict leisure-time walking.

Methods

Participants were a random sample (N = 358) of Canadian adults who completed measures
of the TPB, planning, perceived neighbourhood environment, and personality at Time
1 and self-reported walking behaviour two months later.

Results

Analyses using structural equation modelling provided evidence that leisure-time walking
is largely predicted by intention (standardized effect = .42) with an additional independent
contribution from proximity to neighbourhood retail shops (standardized effect = .18).
Intention, in turn, was predicted by attitudes toward walking and perceived behavioural
control. Effects of perceived neighbourhood aesthetics and walking infrastructure
on walking were mediated through attitudes and intention. Moderated regression analysis
showed that the intention-walking relationship was moderated by conscientiousness
and proximity to neighbourhood recreation facilities but not planning.

Conclusion

Overall, walking behaviour is theoretically complex but may best be addressed at a
population level by facilitating strong intentions in a receptive environment even
though individual differences may persist.

Background

Physical activity (PA) promotion is a public health priority. PA itself, however,
is a collection of behaviours and the promotion of specific modalities may be important.
Walking behaviour has received recent attention based on its physical [1,2] and psychological [3] health benefits and its high preference in terms of activity choice among adults
[4]. These aspects suggest that promotion of regular walking should be the primary focus
of population-based PA promotion efforts.

PA promotion should be theory-based [5,6]. One theory that has been extensively validated in the PA domain is Ajzen's [7] theory of planned behaviour (TPB) [8]. The TPB proposes that the final pathway to behaviour is intention: one's overall
motivation to perform the behaviour. Intentions, however, can only be carried out
in a receptive environment over which the person has control. An objective measure
of control is elusive, but perceived behavioural control (PBC) is often a good proxy
measure of actual control [7,9]. Intention, in turn is thought to be influenced by affective (e.g., evaluation of
the enjoyment of performing the behaviour) and instrumental (e.g., evaluation of the
benefit of performing the behaviour) attitudes, subjective norm (e.g., evaluation
of the perceived approval from others to perform the behaviour) and PBC (i.e., perception
of capability to perform the behaviour when motivation is assumed [10]).

Evaluation of the TPB for predicting walking has been scant. Three studies [11-13] have evaluated the TPB and walking and these show relatively similar results to general
PA meta-analysis in terms of intention-behaviour relations [8]. Rhodes et al. [11], however, showed that PBC was not related to walking whereas the findings of Eves
et al. [12] and Scott et al. [13] suggested that attitude was not a predictor of walking intention or behaviour. The
difference in findings may be from geographical variation (Western Canada vs. U.K.),
measurement differences (general walking vs. leisure-time walking), or sampling fluctuations.
Clearly, more work on the TPB applied to walking is needed.

An understanding of walking may also benefit from adding breadth and depth to the
TPB model and approaches to integrating PA correlates are advocated [14,15]. TPB proposes that variables external to the model should be mediated via its constructs
of attitude, subjective norm, and PBC when considering their respective associations
with behaviour [7]. In addition, external factors may moderate the TPB model. Of particular interest
in this regard is the intention-behaviour relationship [16]. An understanding of moderators of the intention-behaviour link is very important
because a majority of the population reports positive PA intentions but discordant
actual PA [17]. Three factors at different theoretical levels of abstraction that have all shown
application to augment the TPB are the perceived environment, personality, and action
planning/implementation intentions.

Environmental factors are often a focus in walking related research [18]. This literature has some mixed findings, but almost all studies have converged on
the importance of proximity to amenities (e.g., markets, retail stores) and the perceived
aesthetics of the neighbourhood (e.g., attractive scenery, well-maintained homes)
as the key correlates of walking [18-22]. The integration of these environmental factors with social cognitive constructs,
however, is limited at present [11,23-25]. The only study to include the perceived environment within a TPB model to predict
walking found that these perceived environment factors associated with walking (i.e.,
neighbourhood aesthetics, proximity to retail) were mediated by attitudes [11]. Therefore, the tenet of the TPB in terms of mediation of behaviour of "outside"
factors was supported. Also, perceived proximity to recreation moderated intention-walking
relations, with those perceiving a closer proximity showing a larger intention-walking
relationship than those who reported being farther away from recreation infrastructure.
These results suggest that the environment may affect walking behaviour through attitudes
and moderate the intention behaviour gap. Still, the finding requires replication.

Another factor that has received recent attention in the PA domain with the TPB is
personality [26]. Personality is generally defined as stable individual differences in thoughts, feelings,
and actions [27] and a recent meta-analytic review of PA and personality found that extraversion (tendency
to show positive disposition, be sociable and lively, etc.), and conscientiousness
(tendency to be orderly, self-disciplined, etc.) are positive correlates of PA while
neuroticism (tendency to show negative disposition, self-reproach, etc.) is negatively
correlated [28]. Research integrating the TPB with personality and PA has generally found a failure
of the TPB to fully mediate extraversion or conscientiousness [28]. Those study authors have suggested that the stability of personality may augment
the more transient predictive ability of social cognitions on PA across time. Further,
conscientiousness may moderate the intention-behaviour relationship (conscientious
individuals displaying stronger intention-PA associations than their less conscientious
counterparts) [28,29]. Still, almost no research has evaluated personality and walking. Early work by Howard
et al. [30] found that extraversion was correlated with more vigorous intensity forms of PA and
was not related to walking for exercise. Additional research focusing on walking and
personality, and a test of whether conscientiousness moderates the intention-walking
relationship is warranted.

Finally, a construct receiving considerable attention and support in the health behaviour
domain is planning [31-34]. It has been suggested by Gollwitzer and colleagues [31,35] that models like the TPB are motivational in nature, but specific volitional plans
(e.g., if...then, when, why, where, how) may be necessary to translate intentions
into behaviour. Thus, planning may add depth to the TPB framework by acting as a mediator
between intention and behaviour or moderate intention-behaviour relations. Research
on planning and PA in the TPB has shown results in support of this theorizing [e.g.,
[32,33,36]], but not all studies have shown this distinction [33,34]. Research is needed to evaluate the addition of a planning construct when understanding
regular walking.

Therefore, the purpose of this study was to incorporate personality, the perceived
environment, and planning into a TPB framework to predict leisure-time walking. Based
on prior research, it was hypothesized that the perceived environment, most notably
neighbourhood aesthetics and proximity to retail shops, would be correlates of walking
but mediated through attitudes about walking (and subsequent intention to walk). Personality
constructs of extraversion, neuroticism, and conscientiousness were expected to be
unrelated to walking based on prior work [30] and thus not of utility in an integrated TPB model, and planning was hypothesized
to act as a mediator of intention and walking relations [33]. Further, based on prior work [11,29,33,37,38], we hypothesized that the perceived proximity to recreation infrastructure, planning,
and conscientiousness would moderate the intention-walking relationship.

Method

Participants and design

Participants for this study were residents of British Columbia (BC), Canada aged 18
or greater. A random sample of 1500 addresses within BC was obtained from Dominion
Directories (SuperPages Telephone Company). In February 2005, questionnaires approved
by the University of Victoria's Human Research Ethics Board were mailed to the 1500
potential participants. Of the original 1500 questionnaires, 222 envelopes were returned
unopened because the resident had moved (n = 208) or was recently deceased (n = 14),
and 232 questionnaires were returned completed. Of the possible 1046 remaining participants,
a second mailing of a post card reminder and questionnaire [39,40] was sent out two weeks later in which an additional 126 questionnaires were returned.
Thus, a total of 358 participants (28% of eligible participants) completed and returned
the questionnaire. A second follow-up mail-out to these 358 participants was conducted
two months after receipt of their completed survey. Of these participants, 203 individuals
completed and sent back the follow-up questionnaire comprised of a measure of walking
over the past two months (57% follow-up rate).

Of the 358 participants at baseline, 51% were males and 49% were females with a mean
age of 57.0 (SD = 14.6) and 50.6 (SD = 16.9) respectively. Respondents reported themselves
as well-educated; 49.2% had at least a Bachelors degree or certificate, which is above
the 35% reported during the Census of 2001 [41]. Of those reporting race (n = 334), 80.9% were Caucasian which is very close to the
BC census of 78.6% [41]. Other participant characteristics were similar to the general population of British
Columbia. Only 2.3% were unemployed, with 35.8% being retired, 1.1% attending College
or University, 54.3% employed, and 2.5% on leave. Annual family income showed 60.7%
had a household income over 40,000 CDN per year, which is the BC median [41]. Finally, 65.3% of participants were married/common-law, 22.9% were separated/widowed,
and 11.9% reported themselves as single.

For health indicators, 10% of the sample were smokers, 23% reported having high cholesterol,
2.9% had a stroke, 5.1% reported having a heart attack in the past, 24.5% had high
blood pressure, 9.4% had diabetes (64.5% type 2), 8.6% were cancer survivors, and
the mean BMI was 25.71 (SD = 4.59). In terms of physical activity, 17% were aware
of Health Canada's Guide to Healthy Active Living, which is similar to prior research
in Canada [42]. Finally, using the Godin Leisure-Time Questionnaire [43] to measure physical activity, 48.8% were meeting Canada's physical activity guidelines
[44] which is lower than the 58% reported for the province [4]. These data have also been previously reported in a study focused on the TPB belief-level
constructs [45].

Instruments

Perceived environment characteristics

were based on a set of items from the Neighbourhood Environment Walkability Scale
(NEWS)[46,47] and the International Physical Activity Prevalence Study Environmental Survey Module
(IPAPSEM)[48] that have been used to predict walking in prior research [11]. Measurement of the perceived environment is relatively unstandardized at present,
but these measures and previous research [18] highlight proximity to retail or recreation, aesthetics, crime, traffic, and walking
infrastructure quality as key characteristics. We decided to follow the IPAPSEM approach
of clear (i.e., high face validity) single item indicators for each characteristic.
This decision was predicated on the overall length of the NEWS in comparison to the
IPAPSEM, particularly in consideration of the other measures included in this survey,
but with some preference for NEWS items. Thus, proximity was assessed with the items:
(1) "Many shops, stores, markets or other places to buy things I need are within easy
walking distance of my residence" (retail), and (2) "My neighbourhood has several
free or low cost recreation facilities, such as parks, walking trails, bike paths,
and recreation centers" (recreation). Walking infrastructure quality was measured
by the item: "There are well-maintained sidewalks on most of the streets in my neighbourhood,"
and neighbourhood aesthetics was measured using the item: "There are many attractive
natural sights in my neighbourhood (such as landscaping, views...)." Finally, traffic
was measured with the item: "It feels unsafe to walk along the streets in my neighbourhood
because there is so much traffic," and crime was measured with the item: "There is
a high crime rate in my neighbourhood." All items were answered using a four-point
scale from strongly disagree (1) to strongly agree (4) which is similar between the
NEWS and IPAPSEM measures.

Personality

traits of extraversion, neuroticism, and conscientiousness were measured using unipolar
trait markers originally developed and validated by Golberg [49] and further cross-validated by Saucier and Ostendorf (1999). These phenotypic trait
measures have shown identical relationships with PA when compared to genotypic measures
such as the NEO-FFI or EPI [28]. Participants were asked to describe themselves as accurately as possible as they
are typically or generally as compared with persons they know of the same gender and
roughly the same age. Six unipolar markers were used for each trait and rated on 5
point scales from 1 (extremely inaccurate) to 5 (extremely accurate). Internal consistencies
were acceptable for the extraversion (α = .70), conscientiousness (α = .72) and neuroticism
(α = .74) measures.

Walking

was measured using a variant of the Godin Leisure Time Exercise Questionnaire (GLTEQ)
[43,50,51]. This measure has been used in prior walking studies [3,11,52]. The decision to use this adapted GLTEQ was also made because of our inclusion of
general PA in the survey. It made sense to have two very analogous measures of both
PA and walking because similar framing of measures eases response burden and reduces
error [53]. Participants were asked to recall their average weekly walking during their free
time over the past two months. The GLTEQ contains three open-ended PA questions pertaining
to the average frequency of mild, moderate, and strenuous physical activities (with
examples of each) during free time in a typical week. For walking, mild, moderate
and strenuous physical activities were changed to mild (Minimal effort, no perspiration,
a casual walk), moderate (Not exhausting, light perspiration, a good brisk pace) and
strenuous (Heart beats rapidly, sweating, as fast as you could walk) walking respectively.
We also modified the GLTEQ to include an open assessment of average duration. Frequencies
of strenuous (20 minutes+), moderate (30 minutes+), and mild (60 minutes+) were aggregated
to produce a total walking frequency score that corresponds to Health Canada's current
PA recommendations [44].

TPB constructs

were measured using 7-point Likert type questions. For the TPB questions, regular
walking was defined as "walking for at least 30 minutes, at least 4 times or more
per week during your free time." This definition is based Health Canada's recommended
minimum guideline for physical activity.

Attitude

towards regular leisure-time walking was measured using three items that tap the
instrumental (i.e., useful-useless, wise-unwise, beneficial-harmful) component, and
three items that tap the affective (enjoyable-unenjoyable, pleasant-unpleasant, exciting-boring)
component. The response format was a series of 7-point scales (1,7 = extremely, 2,6
= moderately, 3,5 = slightly) and the phrase that preceded these scales was "For me,
regular leisure-time walking over the next 2 months would be...". Cronbach's alpha
coefficients of internal consistency were 0.78 for instrumental attitude and 0.76
for affective attitude.

Subjective norm

was measured by combining two items assessing the injunctive component of subjective
norm and one item that tapped the descriptive component. The items were: (1) "Most
people who are important to me want me to engage in leisure-time walking over the
next 2 months," (2) "Most people whose opinions I value would approve of me engaging
in leisure-time walking over the next 2 months," and (3) "Most people who are important
to me will engage in regular leisure-time walking themselves over the next 2 months"
The combination of these components (injunctive and descriptive) was based on recommendations
of Ajzen [9] and the results of Rhodes and colleagues [54,55]. Cronbach's alpha coefficient of internal consistency was 0.72.

Perceived behavioural control

was measured by three items that have been previously recommended [9,56]. The items were: (1) "In the next 2 months, I have complete personal control over
leisure-time walking if I really wanted to do so," (2) Engaging in leisure-time walking
is mostly up to me in the next 2 months if I wanted to do so," and (3) Engaging in
leisure-time walking over the next 2 months if I wanted to do so would be...". The
first two items were scored on a 7-point scale ranging from 1 (strongly disagree)
to 7 (strongly agree), while the third item was scored from 1 (extremely difficult)
to 7 (extremely easy). The items were standardized before the aggregate measure was
created (α = .86).

Intention and planning

were measured with attention to reducing potential measurement confounds. Based on
the recommendations of Rhodes et al. [34], intention was measured without the use of "intend" and "plan" items and instead
by items that reflect motivation. The two items were: (1) "I am motivated to engage
in regular leisure-time walking over the next 2 months," from 1 (extremely unmotivated)
to 7 (extremely motivated), and (2) "I am determined to engage in regular leisure-time
walking over the next 2 months," from 1 (extremely undetermined) to 7 (extremely determined).
Internal consistency was α = 0.92. Planning was measured using items created by Rise
et al. [36] and further validated by Rhodes et al. [34]. These items were: (1) "I have made plans concerning "when" I am going to engage
in leisure-time walking over the next 2 months," (2) "I have made plans concerning
"where" I am going to engage in leisure-time walking over the next 2 months," (3)
"I have made plans concerning "what" kind of walking (e.g., brisk exercise, casual
social, etc.) I am going to engage in over the next 2 months" and (4) "I have made
plans concerning "how" I am going to get to a place to engage in leisure-time walking
over the next 2 months." These items were scored from 1 (strongly disagree) to 7 (strongly
agree) and internal consistency was acceptable (α = 0.93).

Analyses

Preliminary analyses

Although complete data were available at baseline, 155 participants did not complete
the two month walking assessment. To determine the pattern of missingness surrounding
walking, a dummy variable was created (0 = walking data absent; 1 = walking data present).
Next, this variable was compared on the baseline walking, demographic and TPB variables
via zero-order correlations and χ2 analyses. Results showed that walking missingness was significantly (p < .05) related
to being less educated, living alone, and reporting a lower income. Therefore, the
data were not missing completely at random. Still, it was assumed that the data were
missing at random because the probability of missing a walking data point was not
related to its particular value (i.e. baseline walking), but was dependent upon these
other variables [57]. Missing values were thus imputed using the expectation maximization algorithm [57] in LISREL 8.8. Bivariate correlation and regression results were compared between
the imputed values and values using listwise deletion of missing data to assess the
effect of the missing data procedure. Results using Hotelling's t for dependent correlations
were not significantly different (p < .05), suggesting that the procedure had the
intended effect of increasing power (through the inclusion of the larger N) but not
changing the results.

Analysis plan

Bivariate correlations of perceived environment variables, personality, and TPB constructs
with walking were evaluated. To create parsimony in the integrated path model, only
significant (p < .05) bivariate correlations between personality/perceived environment
and walking were integrated with the TPB to predict walking. This data reduction step
was considered acceptable because a basic bivariate correlation with the dependent
variable of interest (i.e., walking) is necessary to even establish the potential
for mediation [58].

Analyses of the integrated model used structural equation modeling [59] with maximum likelihood estimation and a covariance matrix. Specifically, the environmental/personality
variables were modeled as antecedents of the TPB model, which was subsequently used
to predict walking. The planning variable was modeled as the proximal predictor of
walking with intention and PBC as its respective antecedents [34]. The first indicator of each latent variable was fixed to 1.0 in order to create
a metric scale. Single indicators (i.e., environment variables, walking) were fixed
to 0 error, which is commensurate with ordinary least squares regression analyses.
The environment/personality variables were freed to correlate, and the structural
disturbance terms (residual variance) among TPB variables of affective attitude, instrumental
attitude, subjective norm, and PBC were also freed to correlate amongst each other
as per the tenets of the TPB [7]. Mediation was evaluated by comparing this model to a model where the direct paths
of the environmental/personality variables were freed upon walking in conjunction
with assessment of indirect effects. A nonsignificant (p > .05) χ2 supports mediation [58].

To evaluate whether proximity to recreation, planning, and conscientiousness variables
moderated intention and walking relations, we mean-centered all variables [60] and followed the procedure suggested by Cohen & Cohen [61] using ordinary least squares multiple regression. All hypothesized variables were
analyzed simultaneously. Specifically, intention, planning, conscientiousness, and
proximity to recreation variables were entered into the regression equation first,
and interaction terms were then entered into the regression equation in a second block.
Finally, interpretation of significant interaction effects used Aiken & West's [60] suggested procedure of slope analysis. Type one error was set at p < .05.

Results

Bivariate correlations and descriptives for all variables of interest with walking
can be found in Table 1. All social cognitive constructs correlated with walking and the results were in
the medium effect size range [62]. By contrast, personality variables did not correlate with walking and only perceived
environmental variables of proximity to retail (r = .17), infrastructure quality (r
= .17), and aesthetics (r = .14) were significant correlates.

Because a significant relationship with the dependent variable of walking is required
in mediation analyses, only neighbourhood aesthetics, infrastructure quality and proximity
to retail were carried forward in the subsequent analysis. This next analysis integrated
these three perceived environment variables with the TPB and planning to predict walking.
The model resulted in a moderate fit of the data [χ2 (183) = 716.32; p < .01; CFI = .95; RMSEA = .08] using conventional cut-off criteria and considering
the complexity and size of the model [63]. Still, freeing the direct paths for the perceived environmental variables on walking
improved fit and explained an additional 2% of the variance in walking beyond the
social cognitive constructs (Δχ2 (3) = 18.90; p < .01). The addition of the direct paths of the environmental variables
on intention, however, did not add to the overall fit (Δχ2 (3) = 6.43; p > .05). The final structural model is presented in Figure 1 (covariance results among TPB constructs and environmental variables have been omitted
for illustrative parsimony) and the measurement model with descriptives is presented
in Table 2. The full correlation matrix used for the model can be found in Table 3.

Overall, the measurement model suggested good measurement of the TPB constructs and
planning with significant and large factor loadings. For the structural model, 25%
of the variance in walking was explained. When considering the environmental variables,
only the direct effect of proximity to retail was significant on walking (standardized
effect = .18). This variable, however, had no relationship with the social cognitive
constructs. By contrast, the significant indirect effects for infrastructure quality
(standardized = .09) and neighbourhood aesthetics (standardized = .05) predicting
walking through affective and instrumental attitudes and intention.

These effects, however, did not account for all covariation among TPB constructs of
affective attitude, instrumental attitude, subjective norm, or PBC as correlated structural
disturbance terms of affective and instrumental attitude (standardized effect = .64),
affective attitude and subjective norm (standardized effect = .47), instrumental attitude
and subjective norm (standardized effect = .66), and subjective norm and PBC (standardized
effect = .19) were significant (p < .05). Further, because personality and other environmental variables (not included
in the final structural equation model) may attenuate the effects of infrastructure
quality and aesthetics on attitudes, we also evaluated all these variables simultaneously
as having effects on affective and instrumental attitude in a sub-analysis. The attenuation
effects were present, reducing standardized coefficients by approximately .05, but
they did not alter the significance (p < .05) of infrastructure quality and aesthetics
on attitudes. This suggests that the omission of these variables does not drastically
alter the model.

The social cognitive part of the model showed that intention had the only significant
independent effect (standardized effect = .42) on walking. Affective attitude (standardized
effect = .19), instrumental attitude (standardized effect = .13), and PBC (standardized
effect = .11), however, had significant indirect effects on walking through intention.
Only intention explained planning (standardized effect = .75), but the planning construct
had no subsequent contribution in the model. Affective attitude (standardized effect
= .45), instrumental attitude (standardized effect = .31), and PBC (standardized effect
= .26) subsequently explained 62% of the variance in intention. Subjective norm did
not have an effect on intention independent of the other TPB constructs.

The intention-walking moderator analysis is presented in Table 4. Two of the three possible moderators of the intention-walking relationship were
significant and explained an additional 2% of behaviour. Specifically, proximity to
recreation and conscientiousness moderated the effect of intention on walking [Fchange (3,337) = 2.95, p < .05]. Specific univariate analyses also yielded the same finding with planning showing
no moderator effect [Fchange (1,348) = 0.15, p > .05; R2 = .00], while both proximity to recreation [Fchange (1,347) = 3.79, p < .05; R2 = .01] and conscientiousness [Fchange (1,345) = 3.95, p < .05; R2 = .01] displayed moderator effects on the intention-walking relationship. Further,
when these were entered into a regression equation hierarchically, each explained
1% of the variance. Slope analyses for proximity to recreation and conscientiousness
are presented in Figures 2 and 3 respectively. Interpreting these effects identified that high recreation proximity
resulted in a larger effect of intention on walking (β = .45) than low levels (β =
.12), while participants high (+1 SD) and medium (within 1 SD) in conscientiousness
resulted in a larger effect of intention on walking (β = .49 & .45 respectively) than
low levels (-1 SD; β = .24) of conscientiousness.

Figure 2. Proximity to recreation as a moderator of the intention-walking relationship.

Figure 3. Conscientiousness as a moderator of the intention-walking relationship.

Discussion

This study was the first to attempt an integration of social cognitive, perceived
environment, and personality factors to predict leisure-time walking behaviour. Overall,
the results complimented prior findings in each of these domains while extending the
existing literature on walking.

As hypothesized, the perceived environment, but not personality, was associated with
walking. Specifically, close proximity to retail infrastructure, quality of the walking
infrastructure, and the aesthetics of the neighbourhood were correlates of walking.
These findings parallel general environmental and PA research [18-22,64]. The results for proximity to retail and neighbourhood aesthetics also replicate
prior work focused in British Columbia [11] and the addition of quality walking infrastructure may represent the larger variability
in the sampling frame (i.e., from City of Victoria to the entire province of British
Columbia). Also similar to prior findings with environmental variables, the effect
sizes are in the small range [64]. Small effect sizes are likely important to public health initiatives [65], thus it may be prudent for community planners to consider these factors during neighbourhood
design and revitalization projects.

The null finding for an extraversion-walking relationship replicates prior work [30], but the current study extends this finding to conscientiousness and neuroticism
in a population sample. The indication that walking is unrelated to personality should
be considered a positive, because its impact on human behaviour may be fundamentally
basic/endogenous and difficult to intervene upon [26].

Our main analysis integrated the environmental characteristics salient to walking
within a TPB model that also included a planning construct. Overall, this integrated
model explained 25% of the variance in walking which is similar to basic TPB and PA
[8] and prior walking research [11,12]. Of key interest, perceived proximity to retail predicted walking independent of
the TPB. This result was different from the full mediation of this variable found
in the only other study to apply the TPB [11], but small independent effects of the perceived environment on PA are common in existing
social cognitive and perceived environmental integration research [23-25,66]. The results suggest that participants who live closer to retail may end-up walking
more than originally intended. From a theoretical perspective, the result does not
completely support the mediation tenet of variables "external" to TPB structure. Indeed,
the finding supports a recent model suggested by Fishbein [67] whereby the environment may affect behaviour independent of initial intention. The
hypothesis that some PA is incidental, and dependent upon ones environment, is also
a fundamental tenet of social-ecological models [15]. These results, in concert with most prior work, provide support for this theorizing.

Still, the largest predictor of leisure-time walking was one's intention to walk.
Thus, walking is primarily a motivation-based behaviour. In turn, walking intention
was predicted by affective and instrumental attitudes and PBC, and the effects of
walking infrastructure quality and aesthetics were subsequently mediated by attitudes.
The four studies that have applied the TPB to understanding walking all differ in
their relative contributions from attitude, subjective norm, and PBC constructs [11-13]. Most notable, differences appear to be in the attitude construct, where two studies
have shown attitudes as predictors of walking intent/behaviour (present study and
[11]) and two studies have not [12,13]. This is probably due to measurement differences in the definition of walking (i.e.,
sustained leisure-time walking compared to total walking). Total walking may be largely
incidental to ones appraisal of the behaviour because it is fundamental to mobility
of any kind and for multiple purposes. By contrast, sustained walking during one's
leisure-time would seem more dependent upon the appraisal of the behaviour itself.
Future research is needed to test this conjecture.

Another interesting finding in this integrated model was the null effect of planning
on walking. Planning has had relatively consistent support in the health behaviour
literature as a construct that either augments or even mediates intention-behaviour
relations [31]. This was the first study to apply the planning construct to walking within a TPB
framework, but our findings are almost an exact replication of Rhodes et al. [34]. Three factors may be contributing to this result. First, planning may not be particularly
important to walking independent of motivation itself. Walking is noted for its ease
to physically perform, access, and low cost. Perhaps planning is not as essential
to regular walking because one does not need to overcome these barriers. Some evidence
of this theorizing is also present from the null effect of PBC on walking independent
of intention. Second, from a methodological perspective, intention and planning may
be too collinear to produce unique contributions from each. In these data, intention
and planning correlated r = .76, despite attempts to separate their measurement domains.
Thus, although distinctions between the two constructs can be made theoretically,
participants may not have drawn the same distinctions when responding to the items.
Third, planning may be more critical for the initial behaviour change process and
not a general construct within the TPB model. A vast majority of the population are
in PA stasis (i.e., not changing their PA over short periods of time) [68], and this may attenuate the effect that planning has on those who are actually changing
their walking behaviour. Future research is needed to test these possibilities.

A second purpose of this study was to evaluate planning, conscientiousness, and proximity
to recreation as moderators of the intention-behaviour relationship. All of these
variables have been shown to moderate this relationship in prior work [11,33,38], but they have not been combined to partial-out potential redundancies or to create
an integrated model. As hypothesized, conscientiousness and proximity to recreation
both moderated the intention-walking relationship. The overall size of this effect
was modest (i.e., 2% variance explained) but interactions in survey designs are often
difficult to identify due to limited range in the extreme cells [69]. Thus this effect should be considered meaningful. The effect of close proximity
to recreation facilities and parks on the intention-walking relationship suggests
that those individuals who live closer to recreation have an easier time translating
intentions into action. This may be because close proximity improves the ease of acting
on one's intentions or because it cues people to follow through with their initial
motives. Regardless, the result may have a practical application for regional and
community planners: it appears increasing recreation land-mix may help close the intention-walking
gap.

For conscientiousness, less conscientious individuals showed a lower intention-behaviour
relationship than their moderate and high conscientiousness counterparts. This makes
sense, as conscientious people are considered dutiful, achievement-oriented and orderly;
following through with one's intentions seems a logical course of action for conscientious
people. What was surprising, however, is that planning did not moderate this intention-walking
relationship. Although this null finding has been reported before [34], planning has been cited as the potential mechanism, and even a possible intervention
for the conscientiousness interaction with intention and behaviour [37,38]. This null finding, therefore, does not support prior theoretical conjecture. Although
experimental testing is needed, it may be that conscientiousness affects the intention-behaviour
gap on a basic motivational (e.g., achievement striving) rather than an instrumental
(e.g., organization, planning) level.

This study needs to be interpreted within the context of its limitations. First, the
sampling frame of British Columbia (BC) may not generalize to other regions. BC is
the most active province in Canada [4] and its two major cities feature mild climates. Second, although the sample obtained
for this research was representative of the BC adult population in terms of sociodemographics
[41] and PA [4], the baseline survey response rate was modest and the subsequent attrition rate was
high. If differences in terms of PA cognitions and behaviour exist between those who
completed the questionnaire and those who did not, it will bias our results. Finally,
the walking measure was self-report which can introduce measurement error, particularly
with lower intensity activities like walking. Future replication research using objective
measures (e.g., pedometry, accelerometry) would be desirable.

Conclusion

In summary, a model that integrated the TPB, perceived environment, personality, and
planning provided evidence that leisure-time walking is largely an intention-based
behaviour with an additional independent contribution from one's proximity to neighbourhood
retail shops. Intention, in turn, may be predicated on attitudes about walking and
PBC, and perceived neighbourhood aesthetics and walking infrastructure may affect
walking behaviour through attitudes. The intention-walking relationship, however,
may be moderated by conscientiousness and proximity to neighbourhood recreation facilities.
Overall, walking behaviour may be affected by environmental, social cognitive, and
endogenous individual differences that need to be addressed in intervention efforts.

Competing interests

The author(s) declare that they have no competing interests.

Authors' contributions

RER conceived of the study, crafted the design, coordinated data collection, preformed
the analyses, and drafted the manuscript. CMB contributed to the analyses and drafting
of the manuscript. Similarly, KSC and RCP participated in the design of the study
and helped draft the final manuscript.

Acknowledgements

RER is supported by a scholar award from the Michael Smith Foundation for Health Research,
a new investigator award from the Canadian Institutes of Health Research, and with
funds from the Social Sciences and Humanities Research Council of Canada and the British
Columbia Ministry of Children and Family Development (Human Early Learning Partnership).
CMB is supported by the Canada Research Chair Program. KSC is supported by the Canada
Research Chairs Program and a Research Team Grant from the National Cancer Institute
of Canada with funds from the Canadian Cancer Society and the NCIC/CCS Sociobehavioral
Cancer Research Network. RCP is supported from Salary Awards from the Canadian Institutes
of Health Research and the Alberta Heritage Foundation for Medical Research. We also
acknowledge the hard work of data collection and entry for this project by Carolyn
A. McIntyre.